The present invention is directed to methods and apparatus for chilling in-shell eggs.
Ordinarily, in-shell eggs are collected from the henhouse, washed, graded and separated according to their grading (e.g., S, M, L, XL, Jumbo and the like). Thereafter, optionally, the eggs may be pasteurized to achieve a 3 to 5 log or more reduction in the count of various microorganisms, such as Salmonella enteritidis, associated with in-shell eggs. Whether pasteurized or not, it is necessary to chill the in-shell eggs in connection with their storage and transport to comply with U.S. Department of Agriculture/Food and Drug Administration (USDA/FDA) requirements. Such eggs should be chilled to a temperature, for example, from about 41.degree. F. to about 45.degree. F.
Chilling commercial quantities of in-shell eggs in a refrigeration unit is a slow process. Typically, the refrigeration unit contains chilled air. Without being bound by theory, it is believed that due to the "insulating" properties of air (i.e., poor ability to transfer heat away from, for example, in-shell eggs), it takes 9-10 days or more to chill commercial quantities of in-shell eggs (e.g., 270 or more dozen eggs at a time provided in stack(s) of a plurality of layers of in-shell eggs) in a refrigerator. Because of the slow nature of the refrigeration process, conventional means for chilling eggs are very expensive. During refrigeration, the eggs have to be stored in expensive refrigerated warehouses for extended periods of time. In addition, the prolonged chilling times increase handling costs and reduce the freshness of the eggs.
With respect to optionally pasteurized eggs, chilling may be used to stop further pasteurization thereof. Alternatively (or in addition), eggs may be chilled without pasteurization. Either way, chilling slows down the growth rate of various microorganisms (e.g., pathogenic and non-pathogenic bacteria such as rot bacteria) that are typically present both on the shell and inside the shell of a whole egg, including within the egg albumin and within the egg yolk. Further, chilling also slows down loss of functionality of the eggs.
With regard to pathogens present on and/or inside an in-shell egg, especially a chicken egg, a common pathogen is Salmonella. A variety of other microorganisms may also be present on and/or within in-shell chicken eggs. See E. M. Funk, Pasteurization of Shell Eggs, University of Missouri, College of Agriculture, Agricultural Experiment Station, Research Bulletin 364, pp. 1-28 (May 1943), incorporated herein by reference in its entirety.
While the following comments are directed to chicken eggs, these comments also apply to other types of in-shell eggs.
In the early 1900's, it was appreciated that chicken eggs were pathogenically contaminated on their outer shell. Such contamination was believed to be caused by surface contact with, for example, fecal matter, contaminated animal feed, other contaminated material and the like. It was further believed that in-shell eggs were contaminated within the egg shell by penetration of pathogens through the checks or cracks thereof. It was recognized that microorganisms may enter the pores of an in-shell egg, especially when being chilled in cold water. Further, it has only recently been discovered that bacteria such as Salmonella and, especially, Salmonella enteritidis, enters the egg yolk of an in-shell egg via trans-ovarian transmission (i.e., from the mother to the egg even before the egg is laid by the hen). See M. E. St. Louis et al., The Emergence of Grade A Eggs as a Major Source of Salmonella enteritidis Infections, Journal of the American Medical Association, Vol. 259, No. 14, pp. 2103-2107 (Apr. 8, 1988), incorporated herein by reference in its entirety.
As noted, chilling is used to slow down the growth rate of the various microorganisms that may be present within and/or on in-shell eggs. Chilling may also be used to halt further pasteurization or cooking of eggs once a desired level of pasteurization or cooking has been achieved.
The ability to rapidly chill large numbers of in-shell eggs may be critical to pasteurizing eggs without substantially impairing egg functionality. This is because eggs are typically pasteurized by heating them to a desired temperature range for a desired time. See co-pending Davidson International Application No. PCT/US96/13006 (U.S. application Ser. No. 08/519,184), incorporated herein by reference in its entirety. See also, International Application No. PCT/US95/00254 (WO 95/18538), and U.S. Pat. No. 2,423,233, each incorporated herein by reference in its entirety.
Without rapid chilling of these eggs, they slowly cool towards room temperature. However, the slow cooling may result in the eggs spending too much time at an elevated temperature, causing substantial impairment of egg functionality.
Typically, large volume commercial operations involve transporting one or more batches of, for example, several hundred to thousands of dozens of eggs (e.g., 1,000 to 6,000 dozen eggs) at a time. However, often times such large commercial quantities of in-shell eggs cannot be rapidly chilled together as a single batch sufficient to prevent substantial impairment of egg functionality (e.g., at least about 60 Haugh units per batch) using known refrigeration techniques. Thus, for commercial size operations, in order to halt further pasteurization and avoid substantial impairment of egg functionality, and/or to slow the growth rate of microorganisms associated with in-shell eggs there is a need to rapidly chill a large number of in-shell eggs.
When chilling commercial quantities of in-shell eggs, the ability to maintain their market quality is critically important. For example, the market quality of pasteurized chilled eggs or unpasteurized chilled eggs should be sufficient to market them to the public (for consumption). Thus, chilling of in-shell eggs (with or without prior pasteurization) in a cost efficient manner is paramount, especially for large scale commercial operations to remain efficient, cost-effective and successful. There is, therefore, a need to provide methods and apparatus for rapidly and cost effectively chilling commercial quantities of in-shell eggs.